I have a sleeveless jumper - dress, and you've given me a great idea as to how to make it more wearable by layering over a long cotton tee, for instance.
In addition to my school uniform, jumpers were a popular fashion trend in the 1980's, and well into the early 1990's when jumpers transformed from thick strapped dresses over blouses into spaghetti strapped dresses overtee shirts.